Modelling Reverse Osmosis

After a brief presentation of the principal kinetic and thermodynamic aspects of the theory of reverse osmosis, the present review examines various physicochemical mechanisms of the selectivity of membranes with respect to electrolyte solutions: the electrochemical mechanism, related to the charge of the pore surface; the dielectric exclusion of ions, due to image forces; and the structural mechanism, due to the change in the properties of water in fine hydrophilic pores. Methods for calculating the changes in the standard chemical potentials of ions on entering the membrane phase, and the effects of the Donnan exclusion of ions with allowance for the different charge of the membrane have been described. It has been concluded that it is appropriate to use charged membranes to separate electrolyte solutions at low concentrations. The problem of the transport of solutions through the fine pores of membranes has been formulated, taking account of the equilibrium distribution coefficients of the ions, their mobility, the charge of the membrane, and the phenomenon of concentration polarisation. Routes to the further development of the theory as applied to membranes of different types, different compositions, and solution concentrations have been discussed.
The bibliography contains 84 references.